(VAR N X Y Z X1 X2) (RULES active(terms(N)) -> mark(cons(recip(sqr(N)),terms(s(N)))) active(sqr(0)) -> mark(0) active(sqr(s(X))) -> mark(s(add(sqr(X),dbl(X)))) active(dbl(0)) -> mark(0) active(dbl(s(X))) -> mark(s(s(dbl(X)))) active(add(0,X)) -> mark(X) active(add(s(X),Y)) -> mark(s(add(X,Y))) active(first(0,X)) -> mark(nil) active(first(s(X),cons(Y,Z))) -> mark(cons(Y,first(X,Z))) active(half(0)) -> mark(0) active(half(s(0))) -> mark(0) active(half(s(s(X)))) -> mark(s(half(X))) active(half(dbl(X))) -> mark(X) mark(terms(X)) -> active(terms(mark(X))) mark(cons(X1,X2)) -> active(cons(mark(X1),X2)) mark(recip(X)) -> active(recip(mark(X))) mark(sqr(X)) -> active(sqr(mark(X))) mark(s(X)) -> active(s(mark(X))) mark(0) -> active(0) mark(add(X1,X2)) -> active(add(mark(X1),mark(X2))) mark(dbl(X)) -> active(dbl(mark(X))) mark(first(X1,X2)) -> active(first(mark(X1),mark(X2))) mark(nil) -> active(nil) mark(half(X)) -> active(half(mark(X))) terms(mark(X)) -> terms(X) terms(active(X)) -> terms(X) cons(mark(X1),X2) -> cons(X1,X2) cons(X1,mark(X2)) -> cons(X1,X2) cons(active(X1),X2) -> cons(X1,X2) cons(X1,active(X2)) -> cons(X1,X2) recip(mark(X)) -> recip(X) recip(active(X)) -> recip(X) sqr(mark(X)) -> sqr(X) sqr(active(X)) -> sqr(X) s(mark(X)) -> s(X) s(active(X)) -> s(X) add(mark(X1),X2) -> add(X1,X2) add(X1,mark(X2)) -> add(X1,X2) add(active(X1),X2) -> add(X1,X2) add(X1,active(X2)) -> add(X1,X2) dbl(mark(X)) -> dbl(X) dbl(active(X)) -> dbl(X) first(mark(X1),X2) -> first(X1,X2) first(X1,mark(X2)) -> first(X1,X2) first(active(X1),X2) -> first(X1,X2) first(X1,active(X2)) -> first(X1,X2) half(mark(X)) -> half(X) half(active(X)) -> half(X) )